How to handle overload in cold and hot shock test chambers?

2024-01-05

The overcurrent of this device

Overcurrent refers to the operating state of a motor or electrical accessory that exceeds the rated current, and its operating state is generally less than the short-circuit current, which is 6 times lower than the rated current. The possibility of a short circuit is greater than the current, especially when the motor frequently starts and reverses. In an overcurrent state, if the current value returns to normal before reaching the maximum allowable temperature rise, the electrical accessories can still work normally. However, the impact current caused by overcurrent can damage the motor, and the instantaneous electromagnetic high torque can damage the mechanical transmission components. The power should be cut off immediately.

Short circuit protection device for equipment

Electrical or wiring insulation damage, load short circuit, and wiring errors in electronic control circuits can all cause short circuit faults. The instantaneous fault current generated during a short circuit is ten to dozens of times the rated current. Due to the short circuit current, electrical equipment or distribution lines may be damaged, produce arcs, and even cause fires. Short circuit protection requires cutting off the power supply in a very short time after the short circuit fault occurs, The common method is to connect fuses or low-voltage circuit breakers in series on the line. The operating current of the low-voltage circuit breaker is set to 1.2 times the starting current of the motor.

Overcurrent protection of cold and hot shock test chambers

The overcurrent protection of equipment is usually achieved by overcurrent relays. Connect the overcurrent relay coil in series to the protected circuit. When the current reaches its fixed value, when the overcurrent relay works, it often closes the connector and connects it in series to the branch where the connector coil is located, causing the connector coil to be powered off. Then, the main contact of the interface device in the main circuit is disconnected to timely disconnect the motor power supply.

overload protection

Overloading of the cold and hot shock test chamber refers to the operating state of the motor when the operating current exceeds the rated current but is less than 1.5 times the rated current, within the range of overcurrent operating state. If the motor is overloaded for a long time, the winding temperature rise will exceed the allowable value, insulation aging or damage. Overload protection requires that it is not affected by short-term overload surge current or short-circuit current of the motor, and thermal relays are usually used as overload protection components. When the rated current of the device exceeds 6 times that of the thermal relay, it takes 5 seconds for the device to operate. Before the thermal relay operates, the heating element of the thermal relay may have been burned out. Therefore, when using thermal relays for overload protection, short circuit protection devices such as fuses or low-voltage circuit breakers must be installed simultaneously.

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